A camera calibration operation, which calculates an internal variable and external variable of a camera, is an operation that is required to be performed prior to all operations of calculating Three-Dimensionally (3D) information with a camera.
Although various camera calibration methods have been proposed to date, a camera calibration method with calibration patterns can guarantee the most stable and precise result. However, when a target object to be three-dimensionally reconstructed has a large size, a calibration pattern increases in proportion to the target object. Such a large calibration pattern has limitations in maintenance and management thereof, and moreover, cost expended in manufacturing the large calibration pattern is inversely proportional to the degree of precision, whereby there is a limitation in establishing a camera calibration system.
To overcome such limitations, a method has been proposed that moves a light point with a user's hand to simultaneously capture the light point with a plurality of cameras, and then calibrates the captured images of the light point in a self-calibration scheme. Such a method, however, has a limitation in that time synchronization for capturing the light point among the cameras needs to be achieved.
To overcome limitations that occur in manufacturing a 3D-structure calibration pattern, a method using a calibration pattern of a Two-Dimensional (2D) structure has been proposed. However, the method using the 2D-structure calibration pattern also has a limitation in that the size of the calibration pattern increases in proportion to that of a target to be captured, and has a reduced degree of precision that is required in measuring the relative position of at least one camera disposed around the target.
Therefore, in three-dimensionally reconstructing a large target object using a camera network, there is a need to avoid the increase in a size of a calibration pattern for reconstruction in proportion to a size of the large target object.